Messages in this thread | | | Date | Thu, 29 Jun 2006 09:29:15 +0200 | From | Pavel Machek <> | Subject | Re: Incorrect CPU process accounting using CONFIG_HZ=100 |
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Hi!
> >>>Wouldn't merging the two approaches be in the interest of conserving > >>>cpu resources, while at the same time reflecting an accurate view of > >>>cpu utilization? > >> > >>I think that this would be a worthwhile endeavour once/if > >>sched_clock() is fixed. This is especially the case as CPUs get > >>faster as many tasks may run to completion in less than a tick. > > > >That may not be as simple as it seems. To properly account system v user > >time using the sched_clock we'd have to hook into arch dependant asm > >code to know when entering and exiting kernel context. That is far more > >invasive than the simple on/off runqueue timing we currently do for > >scheduling accounting. > > Yes, it is a problem and we may have to do something approximate like > counting ticks for sys time and subtracting that from the total to get > user time when reporting the times to user space (only a bit more > complex to make sure we don't end up with negative times).
Yes, please.
> How is it intended to handle this problem in the tickless kernel?
Even our "tickless" kernels do tick while CPU is busy. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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